U.S. patent application number 16/426463 was filed with the patent office on 2019-12-05 for force sensor.
The applicant listed for this patent is MiraMEMS Sensing Technology Co., Ltd. Invention is credited to YU-HAO CHIEN, CHIH-LIANG KUO, LI-TIEN TSENG, YU-TE YEH.
Application Number | 20190368951 16/426463 |
Document ID | / |
Family ID | 68693224 |
Filed Date | 2019-12-05 |
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United States Patent
Application |
20190368951 |
Kind Code |
A1 |
TSENG; LI-TIEN ; et
al. |
December 5, 2019 |
FORCE SENSOR
Abstract
A force sensor includes a package substrate, a MEMS-based
device, a package body and a protruding element. The MEMS-based
device is disposed on the package substrate and electrically
connected with the package substrate. The package body encapsulates
the MEMS-based device. The protruding element includes a bump,
disposed on the package body and corresponding to the MEMS-based
device. The force sensor allows a greater assembly tolerance.
Inventors: |
TSENG; LI-TIEN; (Taoyuan
City, TW) ; CHIEN; YU-HAO; (Taipei City, TW) ;
KUO; CHIH-LIANG; (Hsinchu City, TW) ; YEH; YU-TE;
(Hsinchu City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MiraMEMS Sensing Technology Co., Ltd |
Suzhou |
|
CN |
|
|
Family ID: |
68693224 |
Appl. No.: |
16/426463 |
Filed: |
May 30, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01L 1/142 20130101;
B81B 2203/0392 20130101; B81B 2203/0376 20130101; B81B 3/0072
20130101 |
International
Class: |
G01L 1/14 20060101
G01L001/14; B81B 3/00 20060101 B81B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2018 |
CN |
201810537745.X |
Claims
1. A force sensor comprising: a package substrate; a
microelectromechanical system (MEMS)-based device disposed on the
package substrate and electrically connected with the package
substrate; a package body encapsulating the MEMS-based device; and
a protruding element including a bump, disposed on the package body
and corresponding to the MEMS-based device.
2. The force sensor according to claim 1, wherein a top surface of
the bump is a planar surface or a curved surface.
3. The force sensor according to claim 1, wherein the bump is made
of a metallic material or a polymeric material.
4. The force sensor according to claim 1, wherein the bump has a
plate, which is interposed between the bump and the package body or
disposed on the bump.
5. The force sensor according to claim 4, wherein a projection area
of the plate is equal to or smaller than the MEMS-based device.
6. The force sensor according to claim 4, wherein the plate is
interposed between the bump and the package body and covers the
package body.
7. The force sensor according to claim 4, wherein the plate is
disposed on the bump and has a connection leg, which is connected
to the package body.
8. The force sensor according to claim 1, wherein the protruding
element is an extension of the package body.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a force sensor,
particularly to a force sensor allowing a greater assembly
tolerance.
2. Description of the Prior Art
[0002] Since the concept of the microelectromechanical system
(MEMS) emerged in 1970s, MEMS devices have evolved from the targets
explored in laboratories into the objects integrated with
high-level systems. Nowadays, MEMS-based devices have been
extensively used in consumer electronics, and the application
thereof is still growing stably and fast. A MEMS-based device
includes a mobile MEMS component. The function of a MEMS-based
device may be realized through measuring the physical magnitude of
the movement of the MEMS component. The force sensor is an example
of MEMS devices, able to detect a pressing action and/or a pressing
force.
[0003] The existing force sensors include the piezoresistor type
pressure sensor and the capacitor type pressure sensor. Refer to
FIG. 1. In a conventional piezoresistor type pressure sensor, a
plurality of piezoresistors 12 is disposed on a mobile membrane 11.
While a pressing force causes the mobile membrane 11 to deform, the
piezoresistors 12 generate corresponding signals. Refer to FIG. 2.
A conventional capacitor type pressure sensor includes a mobile
membrane 21 and a fixed electrode 22, and the mobile membrane 21 is
disposed opposite to the fixed electrode 22, whereby is formed a
sensing capacitor. The signals generated by the sensing capacitor
are transmitted to an Application Specific Integrated Circuit
(ASIC) chip (not shown in the drawing) through a lead and processed
by the ASIC chip. It is easily understood: a package body 23 is
needed to package and protect the abovementioned components. A
pressing force is conducted through the package body 23 to cause
the deformation of the mobile membrane 21 and make the sensing
capacitor output corresponding signals.
[0004] Refer to FIG. 2 and FIG. 3. Based on the abovementioned
structures, while forces of the same magnitude are applied to
different contact positions on the pressure sensor, the pressure
sensor will output different sensation signals respectively
according to the contact positions. For example, as the contact
position of the force F1 is nearer to the center of the pressure
sensor, the mobile membrane 11 will generate a greater deformation.
Thus, the pressure sensor outputs a greater sensation signal. The
contact positions of the force F2 and the force F3 are farther from
the center of the pressure sensor. Even though the forces F2 and F3
are identical to the force F1, they cause smaller deformations of
the mobile membrane 11 and generate smaller output sensation
signals. The fact that the forces of the same magnitude generate
different output sensation signals is unfavorable to the succeeding
processing and treatment of the signals. In order to make the
output sensation signals more consistent, the manufacturers solve
the problem via limiting the position of the pressing element to a
smaller area close to the center of the pressure sensor. However,
such a measure causes assembly difficulty and decreases assembly
reliability. Accordingly, the industry is eager to develop a force
sensor allowing a greater assembly tolerance.
SUMMARY OF THE INVENTION
[0005] A force sensor is provided therein, wherein a protruding
element is disposed on the package body opposite to the MEMS-based
device, whereby the contact of a pressing element and the
protruding element makes the pressing stress concentrated on the
protruding element, wherefore the force sensor of the present
invention can endure a greater assembly tolerance.
[0006] In one embodiment, the force sensor of the present invention
comprises a package substrate, a MEMS-based device, a package body
and a protruding element. The MEMS-based device is disposed on the
package substrate and electrically connected with the package
substrate. The package body encapsulates the MEMS-based device. The
protruding element includes a bump, disposed on the package body
and corresponding to the MEMS-based device.
[0007] Below, embodiments are described in detail in cooperation
with the attached drawings to make easily understood the
objectives, technical contents, characteristics and accomplishments
of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a diagram schematically showing a conventional
piezoresistor type pressure sensor;
[0009] FIG. 2 is a diagram schematically showing a conventional
capacitor type pressure sensor;
[0010] FIG. 3 is a diagram schematically showing the output signals
corresponding to different contact positions of a conventional
force sensor;
[0011] FIG. 4 is a diagram schematically showing a force sensor
according to a first embodiment of the present invention;
[0012] FIG. 5 is a diagram schematically showing the output signals
corresponding to different contact positions of the force sensor of
the present invention;
[0013] FIG. 6 is a diagram schematically showing a force sensor
according to a second embodiment of the present invention;
[0014] FIG. 7 is a diagram schematically showing a force sensor
according to a third embodiment of the present invention;
[0015] FIG. 8 is a diagram schematically showing a force sensor
according to a fourth embodiment of the present invention;
[0016] FIG. 9 is a diagram schematically showing a force sensor
according to a fifth embodiment of the present invention;
[0017] FIG. 10 is a diagram schematically showing a force sensor
according to a sixth embodiment of the present invention;
[0018] FIG. 11 is a top view schematically showing a protruding
element of the force sensor according to the sixth embodiment of
the present invention; and
[0019] FIG. 12 is a diagram schematically showing a force sensor
according to a seventh embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The present invention will be described in detail with
embodiments and attached drawings below. However, these embodiments
are only to exemplify the present invention but not to limit the
scope of the present invention. In addition to the embodiments
described in the specification, the present invention also applies
to other embodiments. Further, any modification, variation, or
substitution, which can be easily made by the persons skilled in
that art according to the embodiment of the present invention, is
to be also included within the scope of the present invention,
which is based on the claims stated below. Although many special
details are provided herein to make the readers more fully
understand the present invention, the present invention can still
be practiced under a condition that these special details are
partially or completely omitted. Besides, the elements or steps,
which are well known by the persons skilled in the art, are not
described herein lest the present invention be limited
unnecessarily. Similar or identical elements are denoted with
similar or identical symbols in the drawings. It should be noted:
the drawings are only to depict the present invention schematically
but not to show the real dimensions or quantities of the present
invention. Besides, matterless details are not necessarily depicted
in the drawings to achieve conciseness of the drawings.
[0021] Refer to FIG. 4. In one embodiment, a force sensor includes
a package substrate 33, a MEMS-based device, a package body 35 and
a protruding element 36. The MEMS-based device is disposed on the
package substrate 33 and electrically connected with the package
substrate 33. In one embodiment, the MEMS-based device includes a
first substrate 31 and a second substrate 32, wherein the first
substrate 31 includes a fixed electrode 311, a first conductive
contact 312 and a second conductive contact 313. In the embodiment
shown in FIG. 4, the first substrate 31 has a plurality of metal
layers, which are connected with each other by interconnection
structures to form the desired circuit. A portion of the topmost
metal layer is exposed on the surface of the first substrate 31 to
function as the fixed electrode 311, the first conductive contact
312, and the second conductive contact 313. In one embodiment, the
first substrate 31 includes a driver circuit and/or a sensing
circuit. For example, the first substrate 31 may have an analog
and/or digital circuit, which is normally realized by an
Application Specific Integrated Circuit (ASIC). However, the
present invention is not limited by the abovementioned embodiments.
In one embodiment, the first substrate 31 is also called the
electrode substrate. For example, the first substrate 31 may be a
substrate having appropriate rigidity, such as a complementary
metal oxide semiconductor (CMOS) substrate or a glass
substrate.
[0022] The second substrate 32 has a first surface (i.e. the
surface of the second substrate 32, which faces downward), a second
surface opposite to the first surface, and a microelectromechanical
system (MEMS) element 323. The second substrate 32 is disposed over
the first substrate 31 with the first surface being faced to the
first substrate 31 and electrically connected with the first
conductive contact 312 of the first substrate 31. For example, at
least one second connection member 321 of the second substrate 32
and a conductive material 322 on the terminal of the second
connection member 321 are connected with the first conductive
contact 312 of the first substrate 31. In one embodiment, the
second substrate 32 is joined to the first substrate 31 in at least
one of a eutectic bonding method, a fusion bond method, a soldering
method and an adhesive method. The MEMS element 323 and the fixed
electrode 311 are opposite to each other to form a sensing
capacitor. It is easily understood: the movement of the MEMS
element 323 with respect to the fixed electrode 311 would vary the
capacitance of the sensing capacitor. Thus, a sensation signal is
output. The force sensor of the present invention can determine
whether the force sensor is pressed and the magnitude of the
pressing force via measuring the variation of the capacitance of
the sensing capacitor.
[0023] In one embodiment, the first substrate 31 further includes
at least one reference electrode (not shown in the drawing), and
the second substrate 32 further includes at least one reference
element (not shown in the drawing); the reference electrode and the
reference element are opposite to each other to form a reference
capacitor. The persons having ordinary knowledge in the art would
be able to undertake appropriate manipulation to make the reference
capacitor and the sensing capacitor jointly form a differential
capacitor pair, whereby to improve the precision of
measurement.
[0024] The MEMS-based device, which is formed via joining the first
substrate 31 with the second substrate 32, is disposed on the
package substrate 33; a wire bonding process uses a lead 34 to
electrically connect the second conductive contact 313 of the first
substrate 31 with the package substrate 33; the package body 35 is
used to encapsulate the MEMS-based device and the lead 34 for
protecting the abovementioned elements. Thus, the MEMS-based
device, which is encapsulated by the package body 35, can be
electrically connected with the external device through the second
conductive contact 313 of the first substrate 31 and at least one
external conductive contact 331 of the package substrate 33.
[0025] Refer to FIG. 4. The protruding element 36 is disposed on
the package body 35. The protruding element 36 includes a bump 361,
which is corresponding to the MEMS-based device. For example, the
bump 361 of the protruding element 36 is corresponding to the MEMS
element 323. More specifically, the bump 361 of the protruding
element 36 is corresponding to the deformable area of the MEMS
element 323. In one embodiment, the bump 361 of the protruding
element 36 is corresponding to the geometric center of the
deformable area of the MEMS element 323. Refer to FIG. 4 and FIG.
5. Different assembly errors may result in different deviations,
such as the pressing elements A1, A2 and A3 in FIG. 4. As the
protruding element 36 is more sticking out than the package body 35
in the present invention, the pressing stress is concentrated on
the protruding element 36. Thus, the force sensor of the present
invention can still output consistent sensation signals even though
different assembly errors result in different deviations, as shown
in FIG. 5.
[0026] In the embodiment shown in FIG. 4, the top surface of the
bump 361 is a planar surface. However, the present invention is not
limited by the embodiment. Refer to FIG. 6. In one embodiment, the
top surface of the bump 36 is a curved surface. It is easily
understood: the bump 361 may be stuck to the package body 35 by an
adhesive material 37.
[0027] Refer to FIG. 7. The protruding element may be an extension
of the package body 35, such as the protruding portion 351 in FIG.
7. Similarly, the protruding portion 351 is corresponding to the
MEMS-based device. More specifically, the protruding portion 351 is
corresponding to the deformable area of the MEMS element 323. In
one embodiment, the protruding portion 351 is corresponding to the
geometric center pf the deformable area of the MEMS element
323.
[0028] Refer to FIG. 8. In one embodiment, the protruding element
36 includes a bump 361 and a plate 362, wherein the plate 362 is
interposed between the bump 361 and the package body 35. In one
embodiment, the protruding element 36 is an integral element. In
other words, the bump 361 and the plate 362 are fabricated into a
one-piece element. In one embodiment, the protruding element 36 is
made of a metallic material. The projection area of the plate 362
may be equal to or smaller than the deformable area of the MEMS
element 323. In the embodiment shown in FIG. 8, the plate 362 is
corresponding to the deformable area the MEMS element 323. Refer to
FIG. 9. In one embodiment, the projection area of the plate 362 is
larger than the MEMS-based device and covers the upper surface of
the package body 35. Similarly, the top surface of the bump 361 may
be a planar surface (as shown in FIG. 8) or a curved surface (as
shown in FIG. 9). It should be explained: the measurement range of
the force sensor of the present invention, such as a measurement
range of up to 10 Newtons or 100 Newtons, can be adjusted via
modifying the thickness of the MEMS element 323 or modifying the
thickness/material of the package body 35; the measurement range of
the force sensor of the present invention can be also controlled
via modifying the thickness of the plate 323.
[0029] Refer to FIG. 10 and FIG. 11. In one embodiment, the plate
362 may be disposed above the bump 361. In other words, the bump
361 is interposed between the plate 362 and the package body 35.
Thereby, while the plate 362 is pressed, the stress is concentrated
on the bump 361. Thus, the assembly tolerance allowed by the
present invention can be further increased. In one embodiment, the
plate 362 further includes at least one connection leg 363, which
is connected to the package body 35, whereby to prevent the plate
362 from being tilted during pressing.
[0030] Refer to FIG. 12. In one embodiment, the bump 361 may be
formed via dispensing a resin on the package body 35. It is easily
understood: the bump 361 is made of a polymeric material in this
embodiment.
[0031] In conclusion, the present invention is characterized in
that a protruding element is disposed on the package body
corresponding to the MEMS-based device and that the contact of the
pressing element and the protruding element makes the force, which
is originally applied to the pressing element, be concentrated on
the protruding element. Such a structure enables the force sensor
of the present invention to allow a greater assembly tolerance. The
protruding element may include a plate. The measurement range of
the force sensor of the present invention can be controlled via
modifying the thickness of the plate.
[0032] The embodiments have been described above to demonstrate the
technical thoughts and characteristics of the present invention to
make the persons skilled in the art to understand, make, and use
the present invention. However, these embodiments are not intended
to limit the scope of the present invention. Any equivalent
modification or variation according to the spirit of the present
invention is to be also included by the scope of the present
invention.
* * * * *